Method of fabricating implantable pulse generator using wire connections to feedthrough structures

ABSTRACT

In one embodiment, a method of fabricating an implantable pulse generator, comprises: providing a lead body including a plurality of conductors; providing a feedthrough component comprising a plurality of feedthrough pins; hermetically enclosing pulse generating circuitry and switching circuitry within a housing, the feedthrough component being welded to the housing; laser machining each of the plurality of feedthrough pins to comprise a slot along a surface of the respective feedthrough pin; placing a respective conductor from the lead body in the respective slot of each of the plurality of feedthrough pins; and performing welding operations to connect the plurality of conductors of the lead body with the plurality of feedthrough pins of the feedthrough component.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/319,682, filed Mar. 31, 2010, which is incorporated herein byreference.

TECHNICAL FIELD

This application is generally related to a method of fabricating animplantable pulse generator using wire connections to feedthroughstructures.

BACKGROUND

Neurostimulation systems are devices that generate electrical pulses anddeliver the pulses to nerve tissue to treat a variety of disorders.Spinal cord stimulation (SCS) is the most common type ofneurostimulation. In SCS, electrical pulses are delivered to nervetissue in the spine typically for the purpose of chronic pain control.While a precise understanding of the interaction between the appliedelectrical energy and the nervous tissue is not fully appreciated, it isknown that application of an electrical field to spinal nervous tissuecan effectively mask certain types of pain transmitted from regions ofthe body associated with the stimulated nerve tissue. Specifically,applying electrical energy to the spinal cord associated with regions ofthe body afflicted with chronic pain can induce “paresthesia” (asubjective sensation of numbness or tingling) in the afflicted bodilyregions. Thereby, paresthesia can effectively mask the transmission ofnon-acute pain sensations to the brain.

SCS systems generally include a pulse generator and one or more leads. Astimulation lead includes a lead body of insulative material thatencloses wire conductors. The distal end of the stimulation leadincludes multiple electrodes that are electrically coupled to the wireconductors. The proximal end of the lead body includes multipleterminals, which are also electrically coupled to the wire conductors,that are adapted to receive electrical pulses. The distal end of arespective stimulation lead is implanted within the epidural space todeliver the electrical pulses to the appropriate nerve tissue within thespinal cord that corresponds to the dermatome(s) in which the patientexperiences chronic pain. The stimulation leads are then tunneled toanother location within the patient's body to be electrically connectedwith a pulse generator or, alternatively, to an “extension.”

The pulse generator is typically implanted within a subcutaneous pocketcreated during the implantation procedure. In SCS, the subcutaneouspocket is typically disposed in a lower back region, althoughsubclavicular implantations and lower abdominal implantations arecommonly employed for other types of neuromodulation therapies.

The pulse generator is typically implemented using a metallic housingthat encloses circuitry for generating the electrical pulses, controlcircuitry, communication circuitry, a rechargeable battery, etc. Thepulse generating circuitry is coupled to one or more stimulation leadsthrough electrical connections provided in a “header” of the pulsegenerator. Specifically, feedthrough wires typically exit the metallichousing and enter into a header structure of a moldable material. Withinthe header structure, the feedthrough wires are electrically coupled toannular electrical connectors. The header structure holds the annularconnectors in a fixed arrangement that corresponds to the arrangement ofterminals on a stimulation lead.

SUMMARY

In one embodiment, a method of fabricating an implantable pulsegenerator, comprises: providing a lead body including a plurality ofconductors, the plurality of conductors being enclosed in insulativematerial along a first length of the conductors, a second length of theconductors being exposed from the insulative material; providing afeedthrough component comprising a plurality of feedthrough pins;electrically coupling pulse generating circuitry through switchingcircuitry with the plurality of feedthrough pins; hermetically enclosingthe pulse generating circuitry and switching circuitry within a housing,the feedthrough component being welded to the housing; laser machiningeach of the plurality of feedthrough pins to comprise a notch along asurface of the respective feedthrough pin; placing a respectiveconductor of the plurality of conductors in the slot of each of theplurality of feedthrough pins; and performing welding operations toconnect the plurality of conductors of the lead body with the pluralityof feedthrough pins of the feedthrough component.

The foregoing has outlined rather broadly certain features and/ortechnical advantages in order that the detailed description that followsmay be better understood. Additional features and/or advantages will bedescribed hereinafter which form the subject of the claims. It should beappreciated by those skilled in the art that the conception and specificembodiment disclosed may be readily utilized as a basis for modifying ordesigning other structures for carrying out the same purposes. It shouldalso be realized by those skilled in the art that such equivalentconstructions do not depart from the spirit and scope of the appendedclaims. The novel features, both as to organization and method ofoperation, together with further objects and advantages will be betterunderstood from the following description when considered in connectionwith the accompanying figures. It is to be expressly understood,however, that each of the figures is provided for the purpose ofillustration and description only and is not intended as a definition ofthe limits of the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a stimulation system according to one representativeembodiment.

FIGS. 2A-2C respectively depict stimulation portions for inclusion atthe distal end of a lead according to some representative embodiments.

FIGS. 3A-3E depict respective components for creating an electricalconnection from within the housing of a pulse generator to wireconductors of a lead body according to one representative embodiment.

FIG. 4 depicts integration of an intermediate assembly includingfeedthrough structure with one or more housing component(s) of animplantable pulse generator according to one representative embodiment.

FIG. 5 depicts another plurality of components for an intermediateassembly including feedthrough structure for integration with one ormore housing component(s) of an implantable pulse generator according toone representative embodiment.

FIGS. 6 and 7 depict processing of a feedthrough pin according to onerepresentative embodiment.

FIGS. 8-12 depict a series of structures (during various processingsteps) during connection of a wire of a lead body to a feedthrough pinaccording to one representative embodiment.

FIGS. 13-15 depict electrical connection of a respective wire of a leadbody to a feedthrough pin according to another representativeembodiment.

FIGS. 16A-16F depict processing of a feedthrough pin during creation ofan electrical connection with a conductor wire according to onerepresentative embodiment.

DETAILED DESCRIPTION

FIG. 1 depicts stimulation system 100 that generates electrical pulsesfor application to tissue of a patient according to one embodiment. Forexample, system 100 may be adapted to stimulate spinal cord tissue,peripheral nerve tissue, deep brain tissue, cortical tissue, cardiactissue, digestive tissue, pelvic floor tissue, or any other suitabletissue within a patient's body.

System 100 includes implantable pulse generator 150 that is adapted togenerate electrical pulses for application to tissue of a patient.Implantable pulse generator 150 typically comprises a metallic housingthat encloses controller 151, pulse generating circuitry 152, chargingcoil 153, battery 154, far-field and/or near field communicationcircuitry 155, battery charging circuitry 156, switching circuitry 157,etc. of the device. Controller 151 typically includes a microcontrolleror other suitable processor for controlling the various other componentsof the device. Software code is typically stored in memory of the pulsegenerator 150 for execution by the microcontroller or processor tocontrol the various components of the device.

In contrast to many conventional IPGs, pulse generator 150 may compriseattached extension component 170. That is, in lieu of providing aseparate extension lead that is physically placed within a header of anIPG by the surgeon during implant, extension component 170 may bedirectly attached to and may be non-removable from pulse generator 150according to some representative embodiments. Although the integratedextension component 170 is provided for some embodiments, extensioncomponent 170 may be separate according to other embodiments. Thewelding techniques and components disclosed herein may be employedwithin any suitable implantable pulse generating system for applyingpulses to tissue of a patient. Within pulse generator 150, electricalpulses are generated by pulse generating circuitry 152 and are providedto switching circuitry 157. The switching circuit connects to outputwires, traces, lines, or the like (not shown in FIG. 3) which are, inturn, electrically coupled to internal conductive wires (not shown inFIG. 3) of lead body 302 of extension component 170. The conductivewires, in turn, are electrically coupled to electrical connectors (e.g.,“Bal-Seal” connectors) within connector portion 171 of extensioncomponent 170. The terminals of one or more stimulation leads 110 areinserted within connector portion 171 for electrical connection withrespective connectors. Thereby, the pulses originating from pulsegenerator 150 and conducted through the conductors of lead body 172 areprovided to stimulation lead 110. The pulses are then conducted throughthe conductors of lead 110 and applied to tissue of a patient viaelectrodes 111. Any suitable known or later developed design may beemployed for connector portion 171.

For implementation of the components within pulse generator 150, aprocessor and associated charge control circuitry for an implantablepulse generator is described in U.S. Patent Publication No. 20060259098,entitled “SYSTEMS AND METHODS FOR USE IN PULSE GENERATION,” which isincorporated herein by reference. Circuitry for recharging arechargeable battery of an implantable pulse generator using inductivecoupling and external charging circuits are described in U.S. patentSer. No. 11/109,114, entitled “IMPLANTABLE DEVICE AND SYSTEM FORWIRELESS COMMUNICATION,” which is incorporated herein by reference.

An example and discussion of “constant current” pulse generatingcircuitry is provided in U.S. Patent Publication No. 20060170486entitled “PULSE GENERATOR HAVING AN EFFICIENT FRACTIONAL VOLTAGECONVERTER AND METHOD OF USE,” which is incorporated herein by reference.One or multiple sets of such circuitry may be provided within pulsegenerator 150. Different pulses on different electrodes may be generatedusing a single set of pulse generating circuitry using consecutivelygenerated pulses according to a “multi-stimset program” as is known inthe art. Alternatively, multiple sets of such circuitry may be employedto provide pulse patterns that include simultaneously generated anddelivered stimulation pulses through various electrodes of one or morestimulation leads as is also known in the art. Various sets ofparameters may define the pulse characteristics and pulse timing for thepulses applied to various electrodes as is known in the art. Althoughconstant current pulse generating circuitry is contemplated for someembodiments, any other suitable type of pulse generating circuitry maybe employed such as constant voltage pulse generating circuitry.

Stimulation lead(s) 110 may comprise a lead body of insulative materialabout a plurality of conductors within the material that extend from aproximal end of lead 110 to its distal end. The conductors electricallycouple a plurality of electrodes 111 to a plurality of terminals (notshown) of lead 110. The terminals are adapted to receive electricalpulses and the electrodes 111 are adapted to apply stimulation pulses totissue of the patient. Also, sensing of physiological signals may occurthrough electrodes 111, the conductors, and the terminals. Additionallyor alternatively, various sensors (not shown) may be located near thedistal end of stimulation lead 110 and electrically coupled to terminalsthrough conductors within the lead body 172. Stimulation lead 110 mayinclude any suitable number of electrodes 111, terminals, and internalconductors.

FIGS. 2A-2C respectively depict stimulation portions 200, 225, and 250for inclusion at the distal end of lead 110. Stimulation portion 200depicts a conventional stimulation portion of a “percutaneous” lead withmultiple ring electrodes. Stimulation portion 225 depicts a stimulationportion including several “segmented electrodes.” The term “segmentedelectrode” is distinguishable from the term “ring electrode.” As usedherein, the term “segmented electrode” refers to an electrode of a groupof electrodes that are positioned at the same longitudinal locationalong the longitudinal axis of a lead and that are angularly positionedabout the longitudinal axis so they do not overlap and are electricallyisolated from one another. Example fabrication processes are disclosedin U.S. Provisional Patent Application Ser. No. 61/247,360, entitled,“METHOD OF FABRICATING STIMULATION LEAD FOR APPLYING ELECTRICALSTIMULATION TO TISSUE OF A PATIENT,” which is incorporated herein byreference. Stimulation portion 250 includes multiple planar electrodeson a paddle structure.

Although not required for all embodiments, the lead bodies of lead(s)110 and extension component 170 may be fabricated to flex and elongatein response to patient movements upon implantation within the patient.By fabricating lead bodies according to some embodiments manner, a leadbody or a portion thereof is capable of elastic elongation underrelatively low stretching forces. Also, after removal of the stretchingforce, the lead body is capable of resuming its original length andprofile. For example, the lead body may stretch 10%, 20%, 25%, 35%, oreven up or above to 50% at forces of about 0.5, 1.0, and/or 2.0 poundsof stretching force.

The ability to elongate at relatively low forces may present one or moreadvantages for implantation in a patient. For example, as a patientchanges posture (e.g., “bends” the patient's back), the distance fromthe implanted pulse generator to the stimulation target locationchanges. The lead body may elongate in response to such changes inposture without damaging the conductors of the lead body ordisconnecting from pulse generator. Also, deep brain stimulationimplants, cortical stimulation implants, and occipital subcutaneousstimulation implants usually involve tunneling of the lead body throughtissue of the patient's neck to a location below the clavicle. Movementof the patient's neck subjects a stimulation lead to significant flexingand twisting which may damage the conductors of the lead body. Due tothe ability to elastically elongate responsive to movement of thepatient's neck, certain lead bodies according to some embodiments arebetter adapted for such implants than some other known lead bodydesigns. Fabrication techniques and material characteristics for “bodycompliant” leads are disclosed in greater detail in U.S. ProvisionalPatent Application Ser. No. 60/788,518, entitled “Lead BodyManufacturing,” filed Mar. 31, 2006, which is incorporated herein byreference.

Controller device 160 may be implemented to recharge battery 153 ofpulse generator 150 (although a separate recharging device couldalternatively be employed). A “wand” 165 may be electrically connectedto controller device through suitable electrical connectors (not shown).The electrical connectors are electrically connected to coil 166 (the“primary” coil) at the distal end of wand 165 through respective wires(not shown). Typically, coil 166 is connected to the wires throughcapacitors (not shown). Also, in some embodiments, wand 165 may compriseone or more temperature sensors for use during charging operations.

The patient then places the primary coil 166 against the patient's bodyimmediately above the secondary coil (not shown), i.e., the coil of theimplantable medical device. Preferably, the primary coil 166 and thesecondary coil are aligned in a coaxial manner by the patient forefficiency of the coupling between the primary and secondary coils.Controller 160 generates an AC-signal to drive current through coil 166of wand 165. Assuming that primary coil 166 and secondary coil aresuitably positioned relative to each other, the secondary coil isdisposed within the field generated by the current driven throughprimary coil 166. Current is then induced in secondary coil. The currentinduced in the coil of the implantable pulse generator is rectified andregulated to recharge battery 153 by charging circuitry 154. Chargingcircuitry 154 may also communicate status messages to controller 160during charging operations using pulse-loading or any other suitabletechnique. For example, controller 160 may communicate the couplingstatus, charging status, charge completion status, etc.

External controller device 160 is also a device that permits theoperations of pulse generator 150 to be controlled by user after pulsegenerator 150 is implanted within a patient, although in alternativeembodiments separate devices are employed for charging and programming.Also, multiple controller devices may be provided for different types ofusers (e.g., the patient or a clinician). Controller device 160 can beimplemented by utilizing a suitable handheld processor-based system thatpossesses wireless communication capabilities. Software is typicallystored in memory of controller device 160 to control the variousoperations of controller device 160. Also, the wireless communicationfunctionality of controller device 160 can be integrated within thehandheld device package or provided as a separate attachable device. Theinterface functionality of controller device 160 is implemented usingsuitable software code for interacting with the user and using thewireless communication capabilities to conduct communications with IPG150.

Controller device 160 preferably provides one or more user interfaces toallow the user to operate pulse generator 150 according to one or morestimulation programs to treat the patient's disorder(s). Eachstimulation program may include one or more sets of stimulationparameters including pulse amplitude, pulse width, pulse frequency orinter-pulse period, pulse repetition parameter (e.g., number of timesfor a given pulse to be repeated for respective stimset during executionof program), etc. IPG 150 modifies its internal parameters in responseto the control signals from controller device 160 to vary thestimulation characteristics of stimulation pulses transmitted throughstimulation lead 110 to the tissue of the patient. Neurostimulationsystems, stimsets, and multi-stimset programs are discussed in PCTPublication No. WO 01/93953, entitled “NEUROMODULATION THERAPY SYSTEM,”and U.S. Pat. No. 7,228,179, entitled “METHOD AND APPARATUS FORPROVIDING COMPLEX TISSUE STIMULATION PATTERNS,” which are incorporatedherein by reference.

FIGS. 3A-3E depict respective components for creating an electricalconnection from within the housing of a pulse generator to wireconductors of a lead body according to one representative embodiment.

FIG. 3A depicts tube 301. Although shown as a cylindrical structure inFIG. 3A, tube 301 may alternatively possess any other suitablecross-sectional shape (e.g., oval, rectangular, etc.). Tube 301comprises slot 303 and, optionally, flange 302. FIG. 3B depicts endpiece 304. FIG. 3D depicts cap structure 307. Tube 301, end piece 304,and cap 307 are preferably fabricated from the same type of material asemployed for the material of the “can” or housing of pulse generator 150(or, alternatively, a metallurgically compatible material). For example,suitable titanium materials or alloys may be employed for one or more ofthese components according to some embodiments. One or more of tube 301,end piece 304, and cap 307 may be fabricated using suitable metalprocessing techniques. For example, tube 301 may be fabricated usingmetal extrusion with post extrusion processing to create slot 303 andflange 302. Alternatively, metal injection molding may be employed forone or more of tube 301, end piece 304, and cap 307 depending upon thecomponent complexity selected for a specific implementation.

FIG. 3B depicts lead body 306 that includes a plurality of conductorwires 305 within insulative material. At the proximal end of lead body,a length of each conductor wire 305 extends out from the insulativematerial. Lead body 306 may be fabricated using any known or laterdeveloped process. Examples of various lead body fabrication processesare disclosed in U.S. Pat. Nos. 6,216,045, 7,287,366, U.S. PatentApplication Publication No. 20050027340A1, and U.S. Patent ApplicationPublication No. 20070282411A1, which are incorporated herein byreference.

FIG. 3E depicts feedthrough assembly 308. Feedthrough assembly 308comprises a plurality of feedthrough pins 310. Feedthrough pins 310preferably extend through surface 311 from the “back” side of assembly308 to the “front” side of assembly 308. In other embodiments, pins 310need not extend through surface 311 and may be electrically coupled toone or more intermediate electrical components to extend the electricalconnection through to the other side. Feedthrough assembly 300 alsocomprises ferrule 309 about the perimeter of assembly 300. Ferrule 309is shaped to allow ferrule 309 to be attached to slot 303 and to allowthe end of tube 301 to be sealed upon subsequent operations. Feedthroughassembly 308 may be fabricated using conventional techniques forfeedthrough components, although feedthrough assembly 309 comprises adifferent structural design than conventional feedthrough components.

These various components are assembled and welded (e.g., using asuitable laser welding system) together to form an integrated structurebefore being coupled with the housing of pulse generator 150. In oneembodiment, end piece 304 is placed over the insulative material of leadbody 306. Then, tube 301 is likewise placed over the insulative materialof lead body 306. With tube 301 placed sufficiently far along lead body306 that it does not appreciable obstruct operations, the various wires305 of lead body 306 are welded to respective feedthrough pins 310 (onthe back side) of feedthrough assembly 308 (e.g., using the laserwelding system or resistive welding). Non-conductive adhesive may alsobe applied to fix and reinforce the connection between wires 305 andpins 310. Tube 301 is slid back along lead body 306 such that assembly308 is disposed in slot 303. Welding is applied to connect tube 301 toend piece 304 and to connect tube 301 to ferrule 309 of assembly 308(preferably, using the laser welding system). In one specificembodiment, biocompatible polymer material (e.g., silicone or urethanematerials) may be injected or otherwise provided within tube 301 beforetube 301 is sealed through the welding to provide support for wires 305.End cap 307 is then welded to the distal end of tube 301 (preferably,using the laser welding system) to seal tube 301. A medical adhesive mayalso be applied where lead body 306 enters tube 301 to provide anon-hermetic seal.

After performing the welding of these components, intermediate assembly410 is formed (as shown in FIG. 4). Intermediate assembly 410 is thenintegrated with the housing component(s) 420 of pulse generator 150.Specifically, housing component(s) 420 may include an aperture 421 alongone of its surfaces. Intermediate assembly 410 is placed throughaperture 421 with flange 302 placed against the outer surface of housingcomponents 420. Flange 302 is then welded to housing component(s) 420.Upon completion of the welding operations, the internal components ofpulse generator 150 within housing component(s) 420 are hermeticallysealed while being electrically connected to the conductive wires oflead body 306. Connector portion 171 may be provided at the proximal endof lead body 306 before or after intermediate assembly 410 is integratedwith housing component(s) 420. Any suitable known or later developedtechnique for providing connector portion 171 may be employed.

In some embodiments, tube 301 is adapted to provide a frictional fitwith lead body 306. Specifically, tube 301 may provide a sufficientlylarge frictional force to prevent lead body 306 from disengaging fromthe electrical connections formed with pins 310 feedthrough component308 by stretching forces experienced in the patient's body afterimplantation. The interior surface of tube 301 may be adapted to contactlead body 306 for this purpose. The interior diameter of tube 301 may besized to provide sufficient frictional contact. Also, crimping, swaging,or similar operations on tube 301 about lead body 306 may be employed tofacilitate the desired frictional contact.

FIG. 5 depicts components for an intermediate assembly of components foran extension component for integration with a pulse generator housingaccording to another embodiment. As shown in FIG. 5, tube 501 is ahollow, substantially cylindrical structure, although any suitablecross-sectional shape may be employed. Tube 501 includes flange 502 atits distal end. Feedthrough assembly 503 includes a plurality ofconductive pins disposed through ceramic or other suitable insulativematerial 505. Material 505 is surrounded by metallic material of ferrule506. Tube 501 and feedthrough assembly 503 may be fabricated using thesame materials and techniques as discussed above in regard to tube 301and feedthrough assembly 309.

During assembly, tube 501 is initially slid over wire conductors 305 oflead body 306 until tube 501 is sufficiently advanced over lead body 306so that it does not obstruct further operations. The various wireconductors 305 of lead body 306 are coupled to respective pins 504 offeedthrough assembly 503. Pins 504 may extend through material 511 oralternatively may partially extend while being connected to intermediateelectrical components. Tube 501 is the slid into position so that tube501 is set flush against feedthrough assembly 503. Feedthrough assembly503 is welded to tube 501 (e.g., using a laser welding system) to forman intermediate assembly. Tube 501 is then preferably back-filled withsuitable biocompatible material (e.g., silicone). The intermediateassembly is placed within housing component(s) of an implantable pulsegenerator and is welded to the housing components to hermetically sealthe implantable pulse generator.

Conventional feedthrough pins are made using approximately 0.013 inchdiameter solid platinum wire with a melting temperature of 1773° C.Conductor wires 305 for lead bodies 306 commonly include seven strands(48 gauge) of MP35N where six strands are served around one of thestrands thereby resulting in a diameter of approximately 0.003 inches.MP35N has a melting temperature of 1440° C. The thermal diffusivity ofMP35N is approximately 2.82° C.·10⁻⁶ M²/s and the thermal diffusivity ofplatinum is approximately 2.58° C.·10⁻⁵ M²/s, a difference ofapproximately a factor of 10. Additionally, the individual strands ofMP35N can also have a silver core, which has a melting temperature of963° C. Further, the reflectivity of these materials to wavelengths usedby laser welding systems differs. These differences in reflectivity,melting temperature, thermal diffusivity, and diameter of platinum andMP35 stranded wires contribute to the complexity of attaching wires 305to pins 310 using laser welding.

Specifically, during a welding pulse, sufficient energy is presented toeach material to create a melt zone in the metals so the metals willjoin together and solidify into the same mass and produce ametallurgical bond. Since platinum wire used for pins 310 is much largerand has a much greater melt temperature, the platinum wire for pins 310requires more energy to melt than wires 305. If this amount of energy ispresented to the one wire 305 positioned on the surface of acorresponding platinum pin 310 such that the laser impinges directly onthe MP35N material, the wire 305 can pull away from the platinummaterial of pin 310 and no bond will result.

This may be caused by the fine strands of MP35N melting and the surfacetension of the MP35N/silver molten material “balling up” and forming aspheroid shape thereby pulling away form the platinum material of pin310. The process may take place before the platinum melts therebypreventing a bond from occurring. If this occurs, it is possible thatthe exposed portion of wire 305 may be too short to reach the platinumpin 310. If there is a long enough service loop of MP35N wire, the wiremay be repositioned and another weld may be attempted. However,provision of a suitable service loop may be impossible or impractical toemploy for small, precision assemblies.

In some embodiments, one or more adaptations are provided to facilitateelectrical connection of wires 305 of lead body 306 to pins 310. FIGS. 6and 7 depict an adaptation according to one representative embodiment.FIG. 6 depicts feedthrough component 600. Feedthrough component 600comprises platinum pin 601. Pin 601 is surrounded by gold 602 andceramic material 603. Ferrule 604 is applied around ceramic material603. In the state shown in FIG. 6, feedthrough component 600 may befabricated using conventional brazing techniques. After furtherprocessing, feedthrough component 700 is provided as shown in FIG. 7. InFIG. 7, pin 601 of feedthrough component 700 comprises laser machinedslot 701. Alternatively, other surface feature designs could be providedsuch as an “X” or cruciform-type surface feature. In one embodiment, pin601 is initially melted using an infrared (IR) laser. While in itsmolten state, an ultraviolet (UV) laser is employed to laser machine pin601 to obtain the desired surface profile and surface feature(s).

By employing the surface feature, wire 305 may be placed in slot 701during a laser welding operation. The laser energy may be readilyprovided to pin 601 to melt pin 601 without inadvertently causing wire305 to pull away before the welding operation is completed. That is, thelaser energy will impinge upon pin 601 thereby melting pin 601. Wire 305will largely be shielded from direct exposure to the laser energy by itsposition within slot 701 and will melt by conduction of heat from pin601. In an alternative embodiment, a relatively lower amount of laserenergy (e.g., less than the amount applied to pin 601) may be directlyapplied to wire 305 during the welding operation to directly heat wire305 in addition to conductive heating.

Although only one pin 601 is shown in FIGS. 6 and 7, any suitable numberof pins may be processed for a respective device. Also, the pins may bedisposed in any suitable arrangement or array within a feedthroughassembly. Preferably, each pin in the feedthrough assembly is processedas discussed in regard to FIG. 7. Each slot in the pins of thefeedthrough assembly may have the same orientation. Alternatively,selected slots may be oriented or “clocked” differently depending uponany constraints created by a given design of the lead body, thefeedthrough assembly, housing components, or other components.

FIGS. 8-12 depict a series of structures (during various processingsteps) during connection of wire 305 to pin 310 according to onerepresentative embodiment. Selected steps shown in these FIGS. mayemploy conventional forming or stamping methods (e.g., using a fourslide or multi-slide forming tool). In one embodiment, as shown in FIG.8, flat platinum, platinum iridium, MP35N, or other alloy ribbon stock800 is formed using any suitable metal forming and/or processingtechnique(s). Ribbon stock 800 comprises two lateral longitudinalmembers 801 which are joined by medial portion 802. Ribbon stock 800further comprises central extension member 803 which extends away frommedial portion 802. Also, tab members 804 on longitudinal members 801extend above medial portion 802. In one embodiment, dimples 901 areformed in the flat stock 800 to form intermediate component 900 as shownin FIG. 9.

As shown in FIG. 10, the flat stock is bent upon itself to form weldingcomponent 1000. Medial member and central extension member 803 are alsobent to form a curved portion 1001. The concave surface of curvedportion 1001 is adapted to be placed against a feedthrough pin duringsubsequent operations. Extension members 801 are folded over themselvesto be coplanar with the face of dimples 901.

FIGS. 11 and 12 depict respective operations performed while joiningwire 305 to feedthrough pin 310 (shown in FIG. 12) according to onerepresentative embodiment.

Conductor wire 305 is placed between gap between folded longitudinalmembers 802 and tabs 804 as shown in FIG. 11. The size of the gap isselected to accommodate the size of wire 305 and is controlled, duringthe processing steps, by the depth of dimples 901. Tabs 804 are bentover wire 305 as shown in FIG. 12 to produce intimate contact betweenwire 305 with the surface of welding component 1000 and to retain thewire in the gap. In one embodiment, tabs 804 may apply a compressiveforce to wires 305 after tabs 804 are placed in position. Also, tabs 804tend to manage the individual strands of wire 305 which may have atendency to separate from the bundle.

In one embodiment, tabs 804 are adapted to shield wire 305 from directexposure to the laser or resistance welder. The metal of tabs 804 may bedirectly heated into a molten state. For a laser weld, the laser energymay be directly focused on tabs 804 without directly impinging upon wire305. Also, if resistance welding is employed to connect wire 305 to oneor more tabs 804 of welding component 1000, the electrodes of the weldermay be placed against tabs 804. Wire 305 may be heated to its melttemperature indirectly by conduction of heat from one or more of tabs804. In this manner, wire 305 will tend to avoid pulling away andforming a spheroid mass during welding operations. Further, the tabgeometry, size, thickness, and mass may be optimized for welding to wire305. That is, the difference in energy between melting material of arespective tab 804 and melting material of wire 305 will be lessenedthereby reducing the occurrence of wire 305 pulling away during a weldoperation. Further, the mass per unit length of tabs 804 is relativelyclose (as compared to pin 310) to the mass per unit length of wire 305which further assists successful completion of the welding process. Inan alternative embodiment, a smaller amount of laser energy may beapplied to wire 305 during the welding operation to directly heat wire305 in addition to conductive heating.

During connection operations, the presence of two or more tabs 804 mayenable a greater manufacturing yield. Specifically, a welding attemptpreferably occurs on the tab 804 at the distal most portion of wire 305.In the event that the initial weld operation is not optimal, anotherweld attempt may be made on the other or next adjacent tab 804 where thewire 305 is unaffected by the first weld attempt.

The connection of welding component 1000 to pin 310 may occurindependently of the connection of wire 305 to welding component 1000.Welding component 1000 may be connected to pin 310 first or wire 305 maybe connected first at any suitable stage in the overall manufacturingprocess. As shown in FIG. 12, welding component 1000 may be placedagainst a respective feedthrough pin 310. Surface 1001 is preferablyadapted to conform to the diameter of pin 310. Welding component 1000may then be connected to the feedthrough pin 310 using any suitabletechnique including resistive welding and laser welding.

In some embodiments, welding component 1000 further enables tabs 804 tobe “clocked” in any suitable orientation to aid guiding wire 305 intothe gap between the tabs 804. To reduce the overall package size, theability to orient tabs 804 in this manner aids in management of thewires 305, because the various wires 305 of lead body 306 will emanatefrom lead body 306 at different angles.

FIGS. 13-15 depict electrical connection of a respective wire 305 to afeedthrough pin 310 according to another representative embodiment. Asshown in FIG. 13, ribbon clamp component 1300 is formed usingconventional forming or stamping methods (e.g., using a four slide ormulti-slide forming tool). Ribbon clamp component 1300 may be formedfrom platinum, platinum iridium, MP35N, or any other suitable alloy.Ribbon clamp component 1300 comprises curved portion 1301. Ribbon clampcomponent 1300 further comprises flat tab portions 1302 connected to andintegral with curved portion 1301. Flat tab portions 1302 extend outwardin an approximately radial direction. Also, flat tab portions 1302 aredisposed adjacent to each other with gap 1303 provided between theirinterior surfaces. Gap 1303 is preferably sized to fit passage of wire305 between flat tab portions 1302.

In use, a plurality of ribbon clamp components 1300 may be placed aboutrespective feedthrough pins 310 as shown in FIG. 14. Preferably, theinner diameter of curved portion 1301 is selected according to the outerdiameter of feedthrough pins 310 to facilitate this step. The band shapeof curved portion 1301 facilitates locating ribbon clamp components 1300on pins 310 and assists holding them in place so components 1300function in a self-fixturing manner. Flat tab portions 1302 may beplaced in any suitable orientation about pin axis to account fordifferent wire angles from lead body 306 which assists assembly inreduced package-design devices. Each ribbon clamp component 1300 ispreferably welded to its respective pin 310 (e.g., using laser weldingor resistive welding).

A respective wire 305 is also placed within gap 1303 between flat tabportions 1302 of each ribbon clamp component 1300. After placement ofthe wire 305, flat tab portions 1302 may be bent around and against thewire 305 to produce intimate contact and to retain wire 305 in gap 1303.Also, flat tab portions 1302 assist in managing the individual strandsof wire 305 which may have a tendency to separate from the bundle.Preferably, at this point, flat tab portions 1302 apply a compressiveforce to wire 305.

In one embodiment, flat tab portions 1302 are adapted to shield wire 305from direct exposure to the laser or resistance welder. The metal offlat tab portions 1302 may be directly heated into a molten state. For alaser weld, the laser energy may be directly focused on flat tabportions 1302 without directly impinging upon wire 305. Also, ifresistance welding is employed to connect wire 305 to flat tab portions1302 of welding component 1300, the electrodes of the welder may beplaced again flat tab portions 1302. Wire 305 may be heated to its melttemperature indirectly by conduction of heat from flat tab portions1302. In this manner, wire 305 will tend to avoid pulling away andforming a spheroid mass during welding operations. Further, the tabgeometry, size, thickness, and mass may be optimized for welding to wire305. That is, the difference in energy between melting material of flattab portions 1302 and melting material of wire 305 will be lessenedthereby reducing the occurrence of wire 305 pulling away during a weldoperation. Further, the mass per unit length of flat tab portions 1302is relatively close (as compared to pin 310) to the mass per unit lengthof wire 305 which further assists successful completion of the weldingprocess.

The welding of a respective component 1300 to a corresponding pin 310and welding of the component 1300 to a corresponding wire 305 may occurin the same step. Alternatively, the welding of these elements may occurat separate times during the overall device fabrication process.

In other embodiments, welding components 1000 and 1300 providingadditional geometry for reworking bad or failed weld joints.Specifically, the more complex geometry of weld components 1000 and 1300as compared to the cylindrical shape of the feedthrough pin providesadditional locations for further weld attempts to bond the wire to thefeedthrough pin after an unsuccessful initial weld operation.

FIGS. 16A-16F depict processing of feedthrough pin 310 during creationof an electrical connection with conductor wire 305 for a pulsegenerator according to one representative embodiment. The processdescribed for FIGS. 16A-16F is similar to the process discussed forFIGS. 6 and 7 with modifications. Any of the techniques discussed abovemay also be employed for the described below for FIGS. 16A-16F. In FIG.16A, conventional brazed feedthrough pin 310 is shown. The pin 310 maybe cut to a defined length using a UV laser. The laser cutting operationalso preferably creates a flat surface on pin 310. Notch 1601 in pin 310is made along an axis to accommodate a conductor wire as shown in FIG.16B (e.g., using the same UV laser). Posts 1605 are defined on eitherside of notch 1601 by the removal of the material from pin 310 duringthe laser machining operation. In one embodiment, notch 1601 is formedslightly wider (e.g., 0.001 inches wider) than the outer diameter of theconductor wire to be connected to pin 310. In one embodiment, the depthof notch 1601 is approximately twice the outer diameter of the conductorwire to facilitate subsequent operations.

At a suitable time, preferably prior to placement of conductor 305within notch 1601, the end of stranded conductor wire 305 is meltedusing a YAG laser welding system. This welding operation is performedusing a sufficiently large laser beam to include the full diameter ofwire 305. This welding operation forms a single ball of metal at the endof wire 305 from the strands of the DFT wire. The wire 305 is placedwithin notch 1601 of pin 310 with ball 1602 disposed outside the end ofnotch 1601 and adjacent to the exterior surface of pin 310 as shown inFIG. 16C. Posts 1605 are preferably then pinched together to clasp aboutwire 305. The pinching operation preferably applies a compressive forceto wire 305. The distal edges of posts 1605 above wire 305 are broughtinto contact with each other as shown in FIG. 16D.

Using a YAG laser welding system, posts 1605 are seam welded together asalso shown in FIG. 16D. FIGS. 16E and 16F depict different perspectiveviews of pin 310 with wire 305 after the seam welding. The laser pathpreferably extends from just beyond the edge of posts 1065 on thepre-formed ball 1602 of wire 305. As the seam weld progresses, ball 1062and pin 310 will bond making an electrical contact. Also, the seam willsecure posts 1605 about the portion of wire 305 subject to a compressiveforce by posts 1605. Wire 305 is thereby held in place by pinched posts1605 and the laser weld formed by ball 1062 at the end of wire 305 withpin 310. The combination of these characteristics provide a robustelectrical contact and a securely held wire 305.

Alternative laser systems may be employed for any of the embodimentsdiscussed herein. For example, a picosecond or femtosecond laser systemmay be employed to cut and machine pin 310 using extremely short pulses.In lieu of a YAG laser system, a fiber laser may be employed using IRwavelengths. Also, although certain discussions have include exampleorder of processing steps, any suitable order of processing and assemblyof the various components during pulse generator fabrication may beemployed according to some embodiments.

Although certain representative embodiments and advantages have beendescribed in detail, it should be understood that various changes,substitutions and alterations can be made herein without departing fromthe spirit and scope of the appended claims. Moreover, the scope of thepresent application is not intended to be limited to the particularembodiments of the process, machine, manufacture, composition of matter,means, methods and steps described in the specification. As one ofordinary skill in the art will readily appreciate when reading thepresent application, other processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed that perform substantially the same function orachieve substantially the same result as the described embodiments maybe utilized. Accordingly, the appended claims are intended to includewithin their scope such processes, machines, manufacture, compositionsof matter, means, methods, or steps.

The invention claimed is:
 1. A method of fabricating an implantablepulse generator, comprising: providing a lead body including a pluralityof conductors, the plurality of conductors being enclosed in insulativematerial along a first length of the conductors, a second length of theconductors being exposed from the insulative material; providing afeedthrough component comprising a plurality of feedthrough pins;electrically coupling pulse generating circuitry through switchingcircuitry with the plurality of feedthrough pins; hermetically enclosingthe pulse generating circuitry and switching circuitry within a housing,the feedthrough component being welded to the housing; laser machiningeach of the plurality of feedthrough pins to comprise a slot along asurface of the respective feedthrough pin; placing a respectiveconductor of the plurality of conductors in the respective slot of eachof the plurality of feedthrough pins; and performing welding operationsto connect the plurality of conductors of the lead body with theplurality of feedthrough pins of the feedthrough component.
 2. Themethod of claim 1 further comprising: applying laser energy to each ofthe plurality of conductors to melt strands of each conductor to form aball structure at a distal end of the second portion.
 3. The method ofclaim 2 wherein the ball structure at the distal end of each conductorcomprises a diameter greater than a width of each respective slot formedin the plurality of feedthrough pins.
 4. The method of claim 3 whereinthe placing comprises: placing each conductor within the slot of itscorresponding feedthrough pin with its ball structure disposed againstan exterior surface of its corresponding feedthrough pin.
 5. The methodof claim 1 wherein the plurality of conductors have an outer diametersize and wherein a depth of each slot of the feedthrough pins isapproximately twice as large as the outer diameter size of the pluralityof conductors.
 6. The method of claim 5 further comprising: pinchingportions of each feedthrough pin about the slot of the respectivefeedthrough pin to bend the portions to clasp about its correspondingconductor.
 7. The method of claim 5 wherein the performing weldingoperations comprises seam welding the bent portions of each feedthroughpin about its corresponding conductor.
 8. The method of claim 1 furthercomprising: providing non-conductive epoxy over locations where theplurality of conductors are welded to the plurality of feedthrough pins.9. The method of claim 1 wherein the laser machining comprises: meltinga respective feedthrough pin with an infrared (IR) laser; and machininga slot in the melted feedthrough pin using an ultraviolet (UV) laser.10. The method of claim 1 wherein the performing welding operationscomprises: applying a majority of laser energy to the plurality offeedthrough pins and melting the plurality of conductors by conductionof heat from the plurality of feedthrough pins.
 11. The method of claim1 further comprising: providing a connector portion on a distal end ofthe lead body, the connector portion being adapted to electricallyconnect to terminals of a stimulation lead.
 12. The method of claim 1further comprising: providing a tubular structure over the lead bodywith the plurality of conductors extending through the tubularstructure; and welding a ferrule of the feedthrough component to thetubular structure to form an intermediate assembly.
 13. The method ofclaim 12 further comprising: welding the intermediate assembly to one ormore housing components of the implantable pulse generator tohermetically seal the implantable pulse generator.
 14. The method ofclaim 1 wherein the plurality of feedthrough pins are made from platinummaterial and the plurality of feedthrough pins are stranded wire ofMP35N material.